The two scans phaseless technique is a well-known procedure for the characterization of antennas on near-field ranges without need of measuring the phase. Amplitude information over two surfaces compensates for the lack of phase reference. In this paper we propose the combination of spherical and planar surfaces for the application of the two scans technique, together with the application of Wirtinger Flow, a state-of-the art phase retrieval algorithm with high convergence guarantees. The use of different types of surface adds additional information about the field's degrees of freedom, allowing for smaller separation between acquisition surfaces as compared with the 2-sphere techniques. In addition, an initial estimation for the phase is not required. The phase retrieval process is formulated in terms of the Spherical Wave Expansion (SWE) of the antenna under test. The SWE-to-PWE (Plane Wave Expansion) is utilized in order to process the amplitude field on the planar surface. Results for simulated and measured near-field data are shown to demonstrate the potential capabilities of the proposed technique.I.
Single-cut techniques allow for fast antenna characterization by measuring and transforming to far-field individual pattern cuts instead of the full sphere. The cut fields are expanded in a reduced set of cylindrical coefficients, which can be used to accurately compute the far-field in the main pattern cuts for antennas with separable aperture distributions. This communication introduces a fast single-cut nearfield to far-field transformation method using amplitude-only data. The technique is based on the measurement of the near-field magnitude in two concentric cuts and starts an iterative propagation process to retrieve their phases. This technique becomes a fast tool for antenna characterization when one is interested in a few cardinal plane cuts of the antenna and only magnitude measurements are available. The proposed single-cut phaseless technique is tested using simulated and measured data, and it shows its potential for fast and more reliable amplitude-only measurements.
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